Author(s):

Santwana Palai and Subash Chandra Parija

Abstract: Flavonoids have been shown to reduce blood pressure during several pathological conditions. The aim of this work was to investigate the effect of polyphenols such as quercetin, naringenin & EGCG (epigallocatechin-3-gallate) on vasotonic response induced by activation of α₁-adrenergic receptor in pulmonary artery of Capra hircus (PA of Ch). The arterial rings prepared from secondary branch of pulmonary artery of Capra hircus were mounted in automatic organ bath. Isometric contraction induced by PE (10nM - 100µM) under normoxic or hypoxic conditions was recorded in absence or presence of quercetin, naringenin & EGCG. The maximum contractile response (E_max) induced by PE in normoxic rings was almost reduced by more than 80% in hypoxic one. The E_max obtained from PE-induced contractile response curve in presence of quercetin, naringenin, EGCG was reduced by 77%, 87%, 93% in normoxic rings and by 93%, 95%, 95% in hypoxic rings. In conclusion (i) the PA of Ch is sensitive to PE while eliciting contractile response, (ii) the hypoxic state attenuated the α₁-adrenergic receptor activated contractile response, (iii) the relative inhibitory effect of quercetin, naringenin and EGCG on PE contraction is in the order of EGCG> naringenin>quercetin in normoxic state, (iv) in hypoxic PA rings, the inhibitory effect of quercetin, naringenin and EGCG on PE-induced contraction were almost identical (93-95%). In translating the observation, it is recommended that quercetin, naringenin and EGCG could be useful in decreasing vascular resistance of pulmonary artery thereby controlling the pulmonary hypertention.

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